Probably, in the cases where we generally attribute erroneous observations to excess of imagination, the fault really lies in the defective perceptive power. Either the nervous structure lacks sufficient sensitiveness to respond readily to the stimulus, or it lacks the strength to retain the impression. In these respects we commonly note improvement with the amelioration of the general health. It is a question, however, whether, if the stimulus were to make an adequate impression, the impression would not be more effectually retained. Be that as it may, we find persons who observe isolated facts readily enough, and who remember them well, but who learn little thereby, because they lack combining power. Isolated facts are facts to them and nothing more. The notion of _law_ is a thing beyond them, and each fact has to be observed separately. These are just the persons who are unfit to have the charge of nervous invalids, but for some mysterious reason they are just the persons into whose hands nervous invalids most often fall. Perhaps the explanation is, that ready combining power can exist only with a certain amount of sensitiveness of nervous structure, and that the sieves through which we pass our nurses may cast out those who would be of the greatest value in nervous illness, besides tending to lessen the sensitiveness of those that remain.[6] At all events, I have been disappointed to find that women from whom I hoped great things as nurses--women of good organisation, and certainly not of delicate constitution--have broken down completely in the course of their hospital training; whilst women whom I consider positively injurious to any kind of invalid have passed through it triumphantly. The question arises, Are we not unwise so to shape our sieves as to exclude the very people by whom we ourselves would most prefer to be tended in sickness? Will any mere knowledge atone for the loss of that keen intelligence which we recognise in persons of so-called sympathetic disposition?